288 John H. Welsh 



the nematocysts have been able to penetrate the more delicate epithelium of the tongue. 



Numerous attempts have been made to determine the nature of nematocyst toxins. 

 Among the earlier studies were those of Richet, which began in 1902 (for complete 

 report see Richet and Portier (1936)). He isolated two chemically unidentified 

 substances which were named " thalassin " and " congestin ". Two papers summariz- 

 ing much of the earlier work on nematocyst toxins are those of Thiel (1935) and 

 SoNDERHOFF (1936). Recently, Boisseau (1952) has used histochemical procedures 

 in an attempt to identify the capsular contents of nematocysts. 



Coelenterates feed to a considerable extent on crustaceans, and there are close 

 commensal associations between coelenterates and crustaceans (e.g. the several hermit 

 crab-sea anemone pairs). It is natural, therefore, that attention should have been 

 paid to the physiological action of coelenterate extracts when injected into crustaceans. 

 Many interesting observations of this sort have been made by Cantacuzene (1925 a, 

 B, 1926), Cantacuzene and Cosmovici (1925), Cantacuzene and Damboviceanu 

 {1934 A, B, c), Cosmovici (1925 a, b, c, d, e), Rey (1940), Manuta (1943) and others. 

 It is clear that extracts of coelenterate tentacles (the chief nematocyst-bearing struc- 

 tures) have a powerful paralyzing action on crustaceans; also, that a crustacean which 

 lives in close association with a coelenterate develops a resistance to the paralyzing 

 factor(s). 



This paper will summarize a series of observations on the chemical nature and 

 physiological actions of nematocyst toxins. The studies were begun in 1950 and were 

 subsequently carried on as part of a larger study on invertebrate pharmacology. 

 Various localities have provided abundant experimental material, and different 

 portions of the work have been carried out at the Lerner Marine Laboratory, Bimini, 

 British West Indies; the Marine Field Laboratories of the University of Washing- 

 ton, Friday Harbor, Washington; the Plymouth Laboratory, Plymouth, England; 

 and the Bermuda Biological Station. I am indebted to the Directors and Staffs of 

 these Marine Stations for the excellent facilities that have been provided. Work 

 toward the identification of the active materials, mainly by use of paper chromato- 

 graphy, has been done at Harvard University. Because the work at each laboratory 

 was carried out on local representatives, it cannot readily be integrated. It seems best 

 therefore, to give a brief account of the findings made at each location. 



In view of Professor Bigelow's interest in the coelenterates, and especially the 

 scyphomedusae, it is not unfitting that a discussion of nematocyst toxins be included 

 in this volume. It is a privilege to dedicate this paper to one from whom I have 

 learned so much. 



I. OBSERVATIONS MADE AT BIMIN[ (MARCH 27-APRIL 7, 1950) 



The earliest observations in this series were made at Bimini, and concerned mainly 

 the effect of tentacle extracts and certain selected chemicals on the autotomy reflex 

 of a species of fiddler crab. Welsh and Haskin (1939) had found the frequency of 

 dropping of legs in certain crustaceans to be a sensitive indicator of the activity of 

 injected substances, such as acetylcholine and adrenaline. On the assumption that 

 nematocyst substance might act on some step in conduction or transmission of nerve 

 impulses, the autotomy reflex was chosen as an indicator of such action. 



Preliminary tests of three species of fiddler crabs found on North Bimini {Uca 



